166
Circuit 140:
Electrometer with moving-coil instrument
Setup information
Install the two transistors, the ceramic capacitor and two resistors as shown in
2.140.
The seven jumper
wires come next followed by the jumper, which serves as a switch (shown dashed). For your guidance, we
labelled the “switch” with
charge
and
discharge
. Last but not least, connect the moving-coil instrument.
Check the placement on the board again and only then connect the battery.
Components required:
2 x 2N3904 transistors,
1 x 1 k
Ω
resistor,
1 x 4.7 k
Ω
resistor,
1 x 10 nF ceramic capaci-
tor, 1 x moving-coil instru-
ment, 1 x breadboard,
1 x 9V battery with clip
connector
Fig. 2.140:
Electrometer with
moving-coil instrument
Experiment
If everything is wired correctly, switch to
charge
. The moving-coil instrument needle is not moving. In no
time the ceramic capacitor is fully charged. This means that the capacitor’s electrodes have accumulated
as many electrons as possible. In our case, we are talking about one hundred billion of electrons This is a
sheer inconceivable number, and yet, all these electrons can flow through your skin without causing you
any harm. You won’t feel anything at all. The electrical energy contained in these electrons would just be
enough to lift a mass of one thousandth of a gram or one thousandth of a millimetre. That is not much
power, and yet our circuit clearly shows this charging amount. Shift the switch to
discharge
. The needle of
the moving-coil meter moves a tiny bit.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.140.
Содержание ELECTRONICS EXPERIMENTS BOX
Страница 4: ......
Страница 251: ...253 Fig 3 27 Circuit 27 4 seconds switch off delay Fig 3 28 Circuit 28 20 seconds switch off delay...
Страница 258: ...260 Fig 3 42 Circuit 42 Active 8 5V battery monitor Fig 3 43 Circuit 43 Active 7 8V battery monitor...
Страница 260: ...262 Fig 3 46 Circuit 46 Meters for 1 5 V Zener diodes and higher Fig 3 47 Circuit 47 Discreet 2 2V Zener diode...
Страница 261: ...263 Fig 3 48 Circuit 48 Discreet 2 9V Zener diode Fig 3 49 Circuit 49 Discreet 3 7V Zener diode...
Страница 265: ...267 Fig 3 56 Cir cuit 56 Audio limiter Fig 3 57 Circuit 57 Amplifier for a storm detector...
Страница 269: ...271 Fig 3 64 Circuit 64 Stabilizer for 1 9 V Fig 3 65 Circuit 65 Stabilizer for 2 5 V...
Страница 275: ...277 Fig 3 80 Circuit 80 Quiztimer 30 seconds Fig 3 81 Circuit 81 Handy diode tester...
Страница 290: ...292 Fig 3 118 Circuit 118 HF watch dog with LED indicator Fig 3 119 Circuit 119 HF watchdog with moving coil instrument...
Страница 295: ...297 Fig 3 130 Circuit 130 4 seconds switch on delay Fig 3 131 Circuit 131 15 seconds switch off delay...
Страница 298: ...300 Fig 3 136 Circuit 136 NAND gate with moving coil instrument Fig 3 137 Circuit 137 Input level Mixing console...
Страница 300: ...302 Fig 3 140 Circuit 140 Electrometer with moving coil instrument Fig 3 141 Circuit 141 Simple AM Radio...
Страница 315: ...317 Fig 3 179 Circuit 179 HF generator 150 kHz Fig 3 180 Circuit 180 HF generator 420 kHz...
Страница 324: ...326 Fig 3 202 Circuit 202 3 seconds switch on delay Fig 3 203 Circuit 203 7 seconds switch on delay...
Страница 325: ...327 Fig 3 204 Circuit 204 Piercing siren sound with Piezo element Fig 3 205 Circuit 205 Discrete Operational ampli fier...
Страница 328: ...330 Fig 3 210 Circuit 210 Discreet 5 2V Zener diode Fig 3 211 Circuit 211 Discreet 7 4V Zener diode...
